The present invention relates, in general, to semiconductor package handling and, more particularly, to an apparatus and method for detecting the physical orientation of semiconductor packages.
Semiconductor devices and integrated circuits are usually mounted on a die support, electrically connected to conductive leads, and enclosed in a package comprising metal, ceramic, plastic, or the like. The packaged device is then marked to identify the particular type of device enclosed in the package. The packaging process is relatively expensive, often accounting for a surprisingly large percentage of the final cost of the device or integrated circuit. Thus, cost reduction and yield improvement present continuing challenges to semiconductor manufacturers.
Manufacturers require a high degree of automation in all packaging processes to reduce costs. One problem with highly automated processing is that parts are damaged and mis-processed when they are mis-oriented during a particular stage of the packaging or marking processes. For example, when a packaged device is trimmed to electrically separate the conductive leads which extend from the package, mis-orientation results in lead damage that cannot be repaired. In many instances, package mis-orientation results in extensive damage to automated tooling as well. Likewise, when a packaged device is marked, a mis-oriented device is marked incorrectly and must be reworked or scrapped. A need exists for a reliable method for detecting the orientation of semiconductor packages during specific automated assembly operations.
One method for controlling orientation uses machine vision to detect and analyze orientation of the packaged device. Machine vision, however, is very expensive, bulky, and slow. As a result, machine vision is usually reserved for final inspection operations and critical process steps. A less expensive alternative is to use optical sensors that detect and analyze light reflected from a package in an attempt to identify a distinctive signal that corresponds to correct orientation. Although optical sensors are widely used, they require frequent electrical adjustment and provide limited accuracy. As a result, yield losses due to mis-orientation are typically five to ten percent using only optical sensors to detect mis-orientation.
What is needed is an apparatus and method for detecting orientation of semiconductor packages that is highly accurate, fast, and inexpensive. Moreover, an apparatus and method for detecting physical orientation is needed that can be integrated with existing semiconductor package handling equipment, requires little or no adjustment during operation, and is easy to change over for machines that process several different types of packages.